Filamentous fungi are an amazing group of microorganisms able to both degrade and produce a plethora of different compounds. Many fungi have rather modest nutritional requirements, making them very interesting for biotechnological applications, with applications in both submerged and solid-state fermentation. Applications include agriculture, food, and feed, pharmaceutical, pulp and paper, textile industries, as well as a potential for waste valorization. Some of the current and potential products include: ethanol, citric acid, gluconic acid, itaconic acid, lactic acid, fumaric acid, and the fungal biomass as a food or feed, as well as more specific compounds such as enzymes.

Fungal biomass (FB), a by-product of the fermentation processes produced in large volumes, is a promising biomaterial that can be incorporated into poly(lactic acid) (PLA) to develop enhanced biocomposites that fully comply with the biobased circular economy concept. The PLA/FB composites, with the addition of triethyl citrate (TEC) as a biobased plasticizer, were fabricated by a microcompounder at 150 °C followed by injection molding. The effects of FB (10 and 20 wt %) and TEC (5, 10, and 15 wt %) contents on the mechanical, thermal and surface properties of the biocomposites were analyzed by several techniques. The PLA/FB/TEC composites showed a rough surface in their fracture section. A progressive decrease in tensile strength and Young’s modulus was observed with increasing FB and TEC, while elongation at break and impact strength started to increase. The neat PLA and biocomposite containing 10% FB and 15% TEC exhibited the lowest (3.84%) and highest (224%) elongation at break, respectively. For all blends containing FB, the glass transition, crystallization and melting temperatures were shifted toward lower values compared to the neat PLA. The incorporation of FB to PLA thus offers the possibility to overcome one of the main drawbacks of PLA, which is brittleness.

Oyster mushroom (OM) cultivation generates residue that needs to be managed; otherwise, it will be converted into waste. One of the substrates for OM cultivation is the food industry by-product, e.g., a mixture of the brewer’s spent grain (BSG) and wheat bran. This study assesses the OM cultivation residue’s physical and nutritional characteristics as a potential upcycled food ingredient and also considers developing bread from this cultivation residue. The OM was cultivated in a mixture of 55% BSG and 45% wheat bran. After the OM harvest, the cultivation residue (mixture of BSG, wheat bran and mycelium) had a lighter colour and a pleasant aroma compared to the initial substrate. It contained protein (10.8%) and had high niacin (42.4 mg/100 g), fibre (59.2%) and beta-glucan (6.6%). Thiamine, riboflavin and pyridoxine were also present in the cultivation residue. The bread was developed from 50% cultivation residue and 50% wheat flour, and its scores for darkness, dryness, sponginess, sour taste, bitter aftertaste, and aromatic aroma differed from white bread (p-value < 0.05). However, its overall acceptability and liking scores were not significantly different from white bread (p-value > 0.05). Therefore, this OM cultivation residue can be used as a nutritious ingredient; nevertheless, product development should be further explored.

Bread residues represent a significant fraction of retail food wastes, becoming a severe environmental challenge and an economic loss for the food sector. They are, however, an attractive resource for bioconversion into value-added products. In this study, the edible filamentous fungi Neurospora intermedia and Aspergillus oryzae were employed for the production of bioethanol and high-protein biomass by cultivation on enzymatically liquefied bread-waste medium at 150 g/L solids. The fermentation of hydrolysate by N. intermedia resulted in the ethanol titer of 32.2 g/L and biomass yield of 19.2 g/L with ca. 45% protein. However, the fermentation ended with a considerable amount of residual fermentable sugars; therefore, the liquid medium after the first fermentation was distilled and fermented again by two fungal strains (N. intermedia and A. oryzae). The fermentations resulted in the production of additional ethanol and biomass. A. oryzae showed better performance in the production of biomass, while the other strain yielded more ethanol. The final products’ yield ranged 0.29–0.32 g EtOH/g and 0.20–0.22 g biomass/g bread waste depending on the strain used in the second fermentation. The study shows that valorization of bread residuals by fungi is a promising option for the production of biofuels and foodstuff within the circular bioeconomy approach. 

A novel approach of utilizing unsold bread at bakeries as a substrate for the fermentative production of a fungal food product have been developed. Techno-economic feasibility of implementing on-site solid-state fermentation in small-scale bakeries in Sweden to recover 10 kg/day surplus bread using the edible fungus Neurospora intermedia was investigated. Different inoculation to substrate ratios were compared, where 24% of fermented solids to inoculate the next batch presented the best fermentation-benefit ratio. Total capital cost was at its maximum €12,600 that can process 70 tons bread (10 kg/day) in its 20-years lifetime to produce 63 tons of product. Operational costs were dominated by labour cost (53%). Outcomes indicate that the process implementation is economically feasible with an annual net profit of €62,000, rate of return on investment of 18.5%, with a payback-period of 4 years at a discount rate of 7%. According to sensitivity analysis, product-selling price and process bread capacity were critical to the process's economics. Increasing the capacity to 100 kg/day resulted in a substantial increase in net profit value of €5,700,000 compared to the base case scenario. Implementation of this process cast insights on techno-economic performance of a sustainable treatment for surplus bread at bakery-level.

By-products from the food sector with a high load of organic matter present both a waste-handling problem related to expenses and to the environment, yet also an opportunity. This study aims to increase the value of stale bread and brewers spent grain (BSG) by re-introducing these residues to the food production chain by converting them to new protein-enriched products using the edible filamentous fungi Neurospora intermedia and Rhizopusoryzae. After 6 days of solid state fermentation (at 35°C, with a95% relative humidity and moisture content of 40% in the substrate) on stale bread, a nutrient-rich fungal-fermented product was produced. The total protein content, as analyzed by total amino acids, increased from 16.5% in stale sourdough bread to 21.1% (on dry weight basis) in the final product with an improved relative ratio of essential amino acids. An increase in dietary fiber, minerals (Cu, Fe, Zn) and vitamin E, as well as an addition of vitamin D2 (0.89 µg/g dry weight sample) was obtained compared with untreated stale bread. Furthermore, addition of BSG to the sourdough bread with the aim to improve textural changes after fermentation showed promising outcomes. Cultivation of N. intermedia or R. oryzae on stale sourdough bread mixed with 6.5% or 11.8% BSG, respectively, resulted in fungal-fermented products with similar textural properties to a commercial soybean burger. Bioconversion of stale bread and BSG by fungal solid state fermentation to produce a nutrient-enriched food product was confirmed to be a successful way to minimize food waste and protein shortage. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Integrated enzyme production in the biorefinery can significantly reduce the cost of the entire process. The purpose of the present study is to evaluate the production of two hydrolyzing enzymes (amylase and xylanase) by an edible fungus used in the biorefinery, Neurospora intermedia. The enzyme production was explored through submerged fermentation of synthetic media and a wheat-based waste stream (thin stillage and wheat bran). The influence of a nitrogen source on N. intermedia was investigated and a combination of NaNO3 and yeast extract has been identified as the best nitrogen source for extracellular enzyme production. N. intermedia enzymes showed maximum activity at 65 degrees C and pH around 5. Under these conditions, the maximum velocity of amylase and xylanase for starch and xylan hydrolysis was found to be 3.25 U mL(-1) and 14.77 U mL(-1), respectively. Cultivation of N. intermedia in thin stillage and wheat bran medium resulted in relatively high amylase (8.86 +/- 0.41 U mL(-1), 4.68 +/- 0.23) and xylanase (5.48 +/- 0.21, 2.58 +/- 0.07 U mL(-1)) production, respectively, which makes this fungus promising for enzyme production through a wheat-based biorefinery.

Waste streams from ethanol and bread production present inexpensive, abundant and underutilized renewable substrates that are highly available for valorisation into high-value products. A combined submerged to solid state fermentation strategy was studied using the edible filamentous fungus Neurospora intermedia to biotransform ethanol plant residues 'thin stillage' and waste bread as substrates for the production of additional ethanol, biomass and a feed product rich in pigment. The fungus was able to degrade the stillage during submerged fermentation, producing 81 kg ethanol and 65 kg fungal biomass per ton dry weight of thin stillage. Concurrently, the second solid state fermentation step increased the protein content in waste bread by 161%. Additionally, 1.2 kg pigment per ton waste bread was obtained at the best conditions (6 days solid state fermentation under light at 95% relative humidity at 35 °C with an initial substrate moisture content of 40% using washed fungal biomass to initiate fermentation). This study presents a means of increasing the value of waste bread while reducing the treatment load on thin stillage in ethanol plants.